Field of the Disclosure
The present disclosure, for example, relates to wireless communication systems, and more particularly to antenna structures for wireless communications.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Communication systems may employ a licensed spectrum, an unlicensed spectrum, or both. The unlicensed millimeter wavelength (mmW) spectrum in the higher gigahertz (GHz) band (e.g., around 28 GHz or around 60 GHz) is becoming a promising technology, for example, for multi-gigabit wireless communication. Compared to other lower frequency systems (e.g., 800 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, etc.), the spectrum around 60 GHz holds several advantages including an increased unlicensed bandwidth, compact size of a transceiver due to small wavelength (about 5 mm), and less interference due to high atmospheric absorption. However, there are several challenges associated with this spectrum, such as reflection and scattering losses, high penetration loss and high path loss, which limit the range of coverage at 60 GHz and may lead to comparatively more line-of-sight for signal propagation and successful communications. To overcome such issues, directional transmission may be employed. Thus, a technique known as beamforming utilizing multi-element antenna arrays may be employed for mmW wireless communication.
Even with beamforming, however, communications using the mmW spectrum may benefit from an antenna structure that is designed particularly for such wavelengths. Conventional antenna structures designed for lower frequencies (e.g., 800 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, etc.) may include a single omnidirectional antenna (sometimes two or three for diversity) and may be unsuitable for mmW spectrum applications.